Coding of routing protocol messages in markup language

ABSTRACT

An implicit routing protocol for content-based networks having a plurality of XML routers includes an XML Link State Protocol and an XML Subscription Management Protocol that routes customer data based on XML content. The XML Link State Protocol and the XML Subscription Management Protocol includes several messages that must be exchanged between XML routers in the network. These messages are encoded using XML.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 USC 119(e) of prior U.S. provisional application Ser. No. 60/530,675 filed Dec. 19, 2003, the contents of which are herein incorporated by reference.

FIELD OF THE INVENTION

This invention relates to content-based networks, and in particular a method coding of routing protocol messages in such networks using a markup language, such as XML.

BACKGROUND OF THE INVENTION

A routing scheme for content-based networks is described in the paper by A. Carzaniga, M. J. Rutherford, A. L. Wolf, A routing scheme for content-based networking, Department of Computer Science, University of Colorado, June 2003, the contents of which are herein incorporated by reference.

In traditional control plane protocols, such as routing protocols or signaling protocols, messages are typically encoded in a raw binary format. That is, a message is defined as a sequence of fields with pre-defined and fixed sizes. Locating a given field in the message is simply a matter of reading data from a fixed offset. The semantics of a field are known in advance to be either numeric (hexadecimal) data, string or an enumerated value.

An example of a prior-art routing protocol utilizing pre-defined fields with fixed sizes is OSPF Version 2, as defined by RFC 2328, “OSPF Version 2”, April 1998, The Internet Society. An example of a routing message from OSPF is shown in FIG. 1. In this encoding format, the example routing message 1 is made up of a number of pre-defined, fixed size fields. For example, the packet type 2 is determined by the second field, where a value of 1 indicates a hello packet. The size of a given field cannot grow without changing the version number 3, which affects backwards compatibility. Moreover, new fields cannot be added, since the hello message has a variable sized list of neighbors 4 (i.e. repeated neighbor fields) at the end of the message. The Packet length 5 is used to determine how many neighbor entries are present.

More recently defined protocols often make use of a more flexible encoding, known as Type-Length-Value (TLV). In these schemes, each message consists of a series of data elements, and each element contains a “type”(which identifies both the field and semantics of the data), a “size” specified in bytes (which allows more flexible parsing of a message, when the tag value is not known by the receiver), and a “value”(the actual data assigned being propagated by this element). FIG. 2 shows an example TLV encoding in the prior art. The type field 11 is 1 octet, and indicates the type of information being encoded. Other names for field 11 is tag or code. The length field 12 indicates the number of octets which appears in the value field 13. The length field 12 is one octet, and the value field 13 contains the number of octets indicated by the length field 12. An example of a routing protocol using TLV encoding is IS-IS, as defined by RFC 1142, “OSI IS-IS Intra-domain Routing Protocol”, Feburary 1990, the Internet Society.

An example IS-IS routing message utilizing TLVs is shown in FIG. 3, as per RFC 1195, “Use of OSI IS-IS for Routing in TCP/IP and Dual Environments”, December 1990, the Internet Society. FIG. 3 shows an example routing message 15, which is a “Level 1 Partial Sequence Numbers PDU”. In this message, the header portion 16 utilizes fixed field definitions similar to the OSPF example of FIG. 1. Field 17 indicates the number of octets in the header portion 16. Field 18 indicates the number of octets in the entire PDU, and the lengh of the variable length fields 19 is determined by field 18 less field 17. The variable length fields 19 is a sequence of TLV-encoded entries, with each entry using the format shown in FIG. 2. This method has similar limitations in the header portion, since fixed fields are utilized. However, the message is extensible through the use of variable length fields 19, using TLV encodings. If the entire message had been encoded with TLVs, including the header portion, then the message would have even further flexibility as described above.

A fundamental requirement of all networking protocols is that they must be extensible. That is, all protocols evolve, and new fields are added to messages or the size of existing fields is changed. Protocols with fixed message formats typically include a “version” field, which is modified to indicate a change in the protocol specification. There is, of course, a problem with backwards compatibility, as software implemented for a previous version of the protocol can not interpret the new message format.

Protocols utilizing TLV encoding are somewhat better suited to dealing with this; as the message parsing code can be designed to ignore “types” that it doesn't understand (i.e. new message fields), and cope with “lengths” that it does not expect (although in many cases this coping is limited, for example, if a software module is designed to expect a 16 bit integer for some value, and instead receives a 32 bit value, it would be forced to truncate, likely introducing a protocol error).

A common interoperability problem introduced by fixed or TLV formatted messages is caused by the different “endian-ness” of various system architectures. Protocols are typically defined as being in “big-endian” format, meaning the most significant bits and bytes are sent first on the network. However, a sloppy implementation of a protocol on a “little-endian” system may lead to the opposite behavior. Often in this case, encoding problems are not detected until two systems of different endian-ness are tested.

Another side effect of both the fixed or TLV formatted messages, is the increased difficulty of debugging network problems. Network sniffers are a common debugging tool, but much of the value of the network sniffer is it is built in protocol parser; that is, its ability to convert from binary messages to human readable form.

SUMMARY OF THE INVENTION

In a broad aspect the invention provides a method of controlling communication networks including a plurality of network elements, comprising encoding control plane protocol messages using a markup language; and transferring said encoded messages between said network elements.

In one embodiment the invention employs an Implicit Routing Protocol (IRP), which consists of the XML Link State Protocol (XLSP) and the XML Subscription Management Protocol (XSMP), which routes customer data based on Extensible Markup Language (XML) content. The IRP consists of several messages that must be exchanged between XML routers in the network. The encoding of those messages is accomplished using XML, which ensures that the protocols are forward extensible. The use of XML also ensures that future versions of the protocol can be made backwards compatible with previously deployed systems.

The definition of XML encoded routing/networking protocol messages allow ease of forward extensibility. Future backwards compatibility of the protocol can be provided by allowing versioning information, and easily implemented parsing rules to be defined.

XML encoding eliminates “endian-ness” concerns from the realm of the protocol implementation (both message formatting and parsing).

The invention also provides an implicit routing protocol for content-based networks including a plurality of XML routers, comprising an XML Link State Protocol and an XML Subscription Management Protocol that routes customer data based on XML content, said XML Subscription Management Protocol comprising IRP (Implicit Routing Protocol) messages that must be exchanged between XML routers in the network, and said messages being encoded using XML.

The invention also provides a content router for use in a content routed network, said router being configured to exchange control messages containing control information with other content routers in the network, and said router further being configured to encode said control information using a markup language.

BRIEF DESCRIPTION OF THE DRAWING

The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 shows an Example Prior Art Routing Message;

FIG. 2 shows an Example Prior Art TLV Encoding;

FIG. 3 shows an Example Prior Art Routing Message Using TLV;

FIG. 4 shows a Neighbor Acquisition Request Message;

FIG. 5 shows a Neighbor Acquisition Response Message;

FIG. 6 shows a Link State Packet Request Message;

FIG. 7 shows a Link State Packet Response Message;

FIG. 8 shows a Link State Database Description Request Message;

FIG. 9 shows a Link State Database Description Response Message;

FIG. 10 shows a Hello Packet Request Message;

FIG. 11 shows a Hello Packet Response Message;

FIG. 12 shows a Register XSMP Node Request Message;

FIG. 13 shows a Register XSMP Node Response Message;

FIG. 14 shows an XML Subscription Database Description Request Message;

FIG. 15 shows an XML Subscription Database Description Response Message;

FIG. 16 shows an XML Subscription Request Message;

FIG. 17 shows an XML Subscription Response Message;

FIG. 18 shows a Subscription Update Request Message (Router to Router);

FIG. 19 shows a Subscription Update Request Message (Subscriber to Router);

FIG. 20 shows a Subscription Update Response Message;

FIG. 21 shows an Add Subscriber Request Message;

FIG. 22 shows an Add Subscriber Response Message;

FIG. 23 shows a Remove Subscriber Request Message;

FIG. 24 shows a Remove Subscriber Response Message; and

FIG. 25 is a diagram of a typical content routed network.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The content routed network shown in FIG. 25 comprises content routers 100 interconnected by links 120. The network is connected to publishers 140 responsible for generating content, which is transferred to the subscribers 160 over the network. Control messages are exchanged between the network elements.

In accordance with embodiments of the invention the control messages are encoded using XML. A detailed explanation of XML can be found in “Extensible Markup Language (XML) 1.0 (Third Edition)”, W3C Recommendation 4 Feb. 2004, W3C (World Wide Web consortium) and “Extensible Markup Language (XML) 1.1”, W3C Recommendation 15 Apr. 2004, W3C, the contents of which are herein incorporated by reference. A description of IRP, including XLSP and XSMP, can be found in co-filed application Ser. No. 60/530,615, the contents of which are herein incorporated by reference.

The following general points describe how control messages between network elements are formatted in accordance with embodiments of the invention:

-   -   1. The first XML tag in each IRP message reflects the type of         the message.     -   2. The first XML tag in each IRP message includes an attribute         indicating the version of the protocol. Versions are specified         in the format {“version=x.y}”, where both x and y are numeric         characters. See below for rules on versioning.     -   3. The remaining elements nested within an IRP message represent         the fields of a given protocol message. Each element may         optionally be tagged with attributes which define the parsing         and backwards compatibility rules for that field:         -   a. {mandatory =TRUE |FALSE}     -   4. Optionally, some fields may be omitted from a message. This         is accomplished simply by not including the XML element         corresponding to that field. The rule for which fields may be         omitted is specific to a given protocol and message. Handling by         the receiver of omitted fields is described below.

The complete list of XLSP messages and associated XML tag name is shown in Table 1 below: TABLE 1 XLSP Messages XLSP Message Outermost XML Tag Name Neighbor Acquisition Request NaRequest Neighbor Acquisition Response NaReponse Link State Packet Request Lsp Link State Packet Response LspResponse Link State Database Description Request Lsdd Link State Database Description Response LsddResponse Hello Packet Request HelloPacket Hello Packet Response HelloPacketResponse

FIG. 4 shows a sample Neighbor Acquisition Request Message 30. The outermost tag 31 in the XML message is the tag “NaRequest”, which indicates the type of message as per Table 1 above. On the “NaRequest” element 31, the attribute “version” 32 indicates that this message has a version number of “1.0”. Embedded elements, such as “senderId” 33, provide the contents of the NaRequest message 30. In the example element “senderId” 33, the value is indicated by the attribute “val” 34, with contents of “ROUTER₁₃ ENDPOINT:HTTP:192.168.1.1:8080”. The senderId 33 also has an attribute “mandatory” 35 with a value of “TRUE”, indicating that the “senderId” 33 is mandatory information. The components of the NaRequest message are shown in Table 2 below. TABLE 2 NaRequest Message Components Tag Attribute Description Mandatory? NaRequest Message's abbreviated name Yes requestId val Sequential request identifier No senderId val The sending router's unique id Yes priority val The router's priority (1 high −> No 4 low) level val The tier level to which the router No belongs deadTime val The router's dead time No

FIG. 5 shows a sample Neighbor Acquisition Response Message 38. The outermost tag 37 is “NaResponse”, which indicates that this message is a Neighbor Acquisition Response. The “isAccepted” element 36 indicates whether the sender of the response message accepted the Neighbor Acquisition Request message. In this example, “isAccepted” 36 indicates that the request was accepted, since the value is 1 (a value of 0 indicates rejection). The components of the NaResponse message are shown in Table 3 below. TABLE 3 NaResponse Message Components Attri- Manda- Tag bute Description tory? NaResponse Message's abbreviated name Yes requestId val The corresponding request's requestId No isAccepted val Boolean value indicating if the Yes relationship has been accepted senderId val The responding router's unique id Yes priority val The responding router's priority No (1 high −> 4 low) Level val The tier level to which the responding No router belongs deadTime val The responding router's dead time No

FIG. 6 shows a sample Link State Packet Request Message 39. The components of the Link State Packet Request Message 39 are shown in Table 4 below. TABLE 4 Link State Packet Request Message Components Attri- Manda- Tag bute(s) Description tory? Lsp Message's abbreviated name Yes RequestId val Sequential request identifier No senderId val The sending router's unique Yes id sourceId val The router's unique id for Yes which the packet originated sequenceNumber val The sequence number assigned Yes to the LSP by the source, which is used to determine whether a received LSP is newer than an instance previously received. linkCosts Tag indicating a list of No zero or more link costs linkCost routerId, The neighbouring router's No cost unique id along with the link's cost

FIG. 7 shows a sample Link State Packet Response Message 40, which is sent in response to a received Link State Packet Request Message. The components of the Link State Packet Response Message 40 are shown in Table 5 below. TABLE 5 Link State Packet Response Message Components Attri- Tag bute Description Mandatory? LspResponse Message's abbreviated name Yes requestId val The corresponding request's No requestId senderId val The responding router's unique Yes id sourceId val The source router id as Yes specified in the request sequenceNumber val The corresponding request's Yes sequence number

FIG. 8 shows a sample Link State Database Description Request Message 41. Notice that this message contains many nested and repeated elements. XML encoding of routing messages allows any level of element nesting, repeated elements, etc. to be handled in a flexible and expandable manner. For example, the top-level tag “Lsdd” 47 contains a number of nested elements, such as “LinkStatePackets” 42. “LinkStatePackets” 42 itself contains a plurality of nested “Lsp” elements 43. The structure allows for any number of nested “Lsp” elements 43 to be present, which is required by the XLSP routing protocol. Within each “Lsp” element 43, there are further nested elements, such as “LinkCosts” 45. “LinkCosts” 45 itself has a plurality of nested “linkCost” elements 46. The nesting described above allows a given Link State Database Description Message 41 to contain a plurality of “Lsp” information 43, and each “Lsp” information 43 can contain a plurality of “linkCost” information 46. This allows the Link State Database Description Mesasge 41 to carry “Lsp” information about a number of XLSP nodes, and for each XLSP node, all the link information for that node can be carried. Using XML as an encoding scheme allows for complex data relationships to be easily modeled and exchanged between routers, as opposed to the prior art routing message encoding schemes of using fixed structures or TLV encodings. The components of the Link State Database Description Request Message 41 are shown in Table 5 below. TABLE 6 Link State Database Description Request Message Components Attri- Tag bute(s) Description Mandatory? Lsdd Message's abbreviated name Yes requestId val Sequential request identifier No senderId val The sending router's unique id Yes LinkStatePackets Tag indicating a list of zero or No more link state packets Lsp Start tag for a link state No packet (refer to Link State Packet Request in Table 4 above.)

FIG. 9 shows a sample Link State Database Description Response Message 50, which is sent in response to a received Link State Database Description Request Message. The components of the Link State Database Description Response Message 50 are shown Table 7 below. TABLE 7 Link State Database Description Response Message Components Tag Attribute Description Mandatory? LsddResponse Message's abbreviated name Yes requestId val The corresponding request's No requestId senderId val The responding router's Yes unique id

FIG. 10 shows a sample Hello Packet Request Message 51. The components of the Hello Packet Request Message 51 are shown in Table 8 below. TABLE 8 Hello Packet Request Message Components Tag Attribute(s) Description Mandatory? HelloPacket Message's abbreviated name Yes requestId val Sequential request identifier No senderId val The sending router's unique id Yes

FIG. 11 shows a sample Hello Packet Response Message 52, which is sent in response to a Hello Packet Request Message. The components of the Hello Packet Response Message 52 are shown in Table 9 below. TABLE 9 Hello Packet Response Message Components Attri- Tag bute Description Mandatory? HelloPacketResponse Message's abbreviated Yes name requestId val The corresponding No request's requestId senderId val The responding router's Yes unique id

The complete list of XSMP messages and associated XML tag name is shown in Table 10 below: TABLE 10 XSMP Messages XSMP Message Outermost XML Tag Name Register XSMP Node Request RegisterXsmpNode Register XSMP Node Response RegisterXsmpNodeResponse XML Subscription Database Description Xsdd Request XML Subscription Database Description XsddResponse Response XML Subscription Request Xsr XML Subscription Response XsrResponse Subscription Update Request SubscriptionUpdate Subscription Update Response SubscriptionUpdateResponse Add Subscriber Request AddSubscriber Add Subscriber Response AddSubscriberResponse Remove Subscriber Request RemoveSubscriber Remove Subscriber Response RemoveSubscriberResponse

FIG. 12 shows a sample Register XSMP Node Request Message 53. Note the use of nested “XsmpNodeInfo” elements 54, which themselves contain nested elements. The components of the Register XSMP Node Request Message 53 are shown in Table 11 below. TABLE 11 Register XSMP Node Request Message Components Attri- Manda- Tag bute(s) Description tory? RegisterXsmpNode Message's abbreviated name Yes senderId val The sending endpoint's unique No id XsmpNodeList Indicate the beginning of a No list of xsmp nodes XsmpNodeInfo Start tag for information No about an xsmp node nodeId val The Xsmp node's unique id No

FIG. 13 shows a sample Register XSMP Node Response Message 55, which is sent in response to a received Register XSMP Node Request Message. The components of the Register XSMP Node Response Message 55 are shown in Table 12 below. TABLE 12 Register XSMP Node Response Message Components Attri- Manda- Tag bute(s) Description tory? RegisterXsmpNodeResponse Message's abbreviated Yes name senderId val The responding Yes router's id isOk val Boolean value indi- Yes cating whether the registration was successful or not

FIG. 14 shows a sample XML Subscription Database Description Request Message 56. Note the use of nested “XsdbRowDescription” elements 57, which themselves contain nested elements. The components of the XML Subscription Database Description Request Message 56 are shown in Table 13 below. TABLE 13 XML Subscription Database Description Request Message Components Attri- Manda- Tag bute(s) Description tory? Xsdd Message's abbreviated name Yes senderId val The sending router's id Yes XsddRows Tag indicates beginning of Yes the list of row descriptions XsdbRowDescription Tag indicates beginning of a Yes row description nodeId val The router id whose XML Yes Subscription Database (XSDB) row is being described firstSeqNum val The sequence number of Yes the first message in XSDB lastSeqNum val The sequence number of Yes the last message in XSDB

FIG. 15 shows a sample XML Subscription Database Description Response Message 58, which is sent in response to a received XML Subscription Database Description Request Message. The components of the XML Subscription Database Description Response Message 58 are shown in Table 14 below. TABLE 14 XML Subscription Database Description Response Message Components Attri- Manda- Tag bute(s) Description tory? XsddResponse Message's abbreviated name Yes senderId val The responding router's id Yes isOk val Boolean value indicating whether Yes the database description was processed successfully or not

FIG. 16 shows a sample XML Subscription Request Message 59. Note the use of nested “XsmpUpdateRequest” elements 60, which themselves contain nested elements. The components of the XML Subscription Request Message 59 are shown in Table 15 below. TABLE 15 XML Subscription Request Message Attri- Manda- Tag bute(s) Description tory? Xsr Message's abbreviated name Yes senderId val The sending router's id Yes reqNodeInfo val Boolean flag indicating Yes interest in node information reqXsdd val Boolean flag indicating Yes interest in a nodes XSDD requests Tag indicates beginning of Yes the list of requests XsmpUpdateRequest Tag indicates beginning of a Yes request nodeId val The router id whose XSDB Yes row is being requested firstSeqNum val The sequence number of the Yes first message being requested lastSeqNum val The sequence number of the Yes last message being requested

FIG. 17 shows a sample XML Subscription Response Message 61, which is sent in response to a received XML Subscription Request Message. The components of the XML Subscription Response Message 61 are shown in Table 16 below. TABLE 16 XML Subscription Response Message Attri- Tag bute(s) Description Mandatory? XsrResponse Message's abbreviated name Yes senderId val The responding router's id Yes isOk val Boolean value indicating whether Yes the request was fulfilled successfully or not

FIG. 18 shows a sample Subscription Update Request Message 62. Note that within the “PacketList” element 63, there can exist a plurality of “NameSpacePacket” elements 64 and a plurality of “SubscriptionPacket” elements 65. Within a “NamespacePacket” element 64, the “prefix” element 66 indicates a unique namespace prefix name, and the “namepace” element 67 indicates the namespace name that is assigned to the prefix. In this example, the prefix “pref1” defined in element 66 is mapped to the namespace “www.pref1.com” in element 67. Refer to “Namespaces in XML”, W3C Recommendation 14 Jan. 1999, World Wide Web Consortium (W3C) and “Namespaces in XML 1.1”, W3C Recommendation 4 Feb. 2004, World Wide Web Consortium (W3C). This allows prefixes to be assigned to namespaces for use in XPath expressions as part of subscriptions. In the “SubscriptionPacket” 65, the “subscription” element 68 contains an “xpe” attribute that defines the subscription string “/pref1:x/y/z”. Note that “xpe” refers to “XPath Expression”. Refer to “XML Path Language (XPath) Version 1.0”, W3C Recommendation 16 Nov. 1999, World Wide Web Consortium (W3C). This subscription uses the previously defined prefix “pref1”. This scheme allows the sending router to send a shared set of prefix definitions which can be used across a large set of subscriptions. The components of the Subscription Update Request Message 62 are shown in Table 17 below. This version of the message is used from one XML router to another XML router. TABLE 17 Subscription Update Request Message (Router to Router) Attri Manda- Tag bute(s) Description tory? SubscriptionUpdate Message's abbreviated name Yes senderId val The sending router's id No subscriberId val The id of the router for which Yes the update applies xsdbFirstSeqNum val The sequence number of the Yes first packet in the XSDB (XML Subscription Database) xsdbLastSeqNum val The sequence number of the last Yes packet in the XSDB PacketList Tag indicates beginning of the Yes list of update packets NamespacePacket Tag indicates beginning of a No namespace packet addFlag val Boolean indicating whether to No add (1) or remove (0) the namespace (default is 1). prefix val The prefix to be associated Yes with the following namespace namespace val The namespace associated with Yes the prefix seqNum val The update packet's sequence Yes number prevSeqNum val The sequence number of the Yes preceding update packet SubscriptionPacket Tag indicates beginning of a No subscription packet addFlag val Boolean indicating whether to No add (1) or remove (0) the namespace (default is 1). isFilter val Boolean indicating whether No subscription acts as a filter (never forward matches) or not (default is 0). Filters are never propagated between routers. subscription xpe The subscription in the form Yes of an XPath string seqNum val The update packet's sequence Yes number prevSeqNum val The sequence number of the Yes preceding update packet

FIG. 19 shows a sample Subscription Update Request Message 70, which is used from a subscriber to an XML router (as opposed to the version above which is used between XML routers). This message can contain a plurality of SubscriptionPacket elements 71, each of which describes one subscription being updated (either added or removed). Within the SubscriptionPacket element 71, the subscription element 72 defines both XML namespaces 73 (of which there can be a plurality or none, and only relate to the subscription element 72) and an xpe 74. In the example subscription element 72, two namespaces have been defined (prefixes “sol” and “google”) and used in the xpe 74. In the example subscription element 75, no namespaces have been defined as the xpe 76 does not use any. While the SubscriptionUpdate message 70 from a subscriber to an XML router does not use a separate definition of namespaces as in message 62 of FIG. 18, that technique could also be used in the messaging from subscribers if there is a number of namespace definitions that could be shared across a large number of subscriptions from a single subscriber. The components of the Subscription Update Request Message 70 used from subscribers to the router are shown in Table 18 below. TABLE 18 Subscription Update Request Message (Subscriber to Router) Manda- Tag Attribute(s) Description tory? SubscriptionUpdate Packets abbreviated name Yes senderId val The sending endpoint's No unique id subscriberId val The id of the subscriber Yes for which the update applies PacketList Tag indicates beginning of Yes the list of update packets SubscriptionPacket Tag indicates beginning Yes of a subscription packet addFlag val Boolean indicating whether No to add (1) or remove (0) the subscription (default is 1). isFilter val Boolean indicating whether No subscription acts as a filter (never forward matches) or not (default is 0, i.e. not a filter) subscription Xpe, The subscription in the Yes namespace form of an Xpath string definitions with namespace definitions (if applicable)

FIG. 20 shows a sample Subscription Update Response Message 80, which is sent in response to a received Subscription Update Request Message (from a router or a subscriber, i.e. a response to message 62 of FIG. 18 or message 70 of FIG. 19). The components of the Subscription Update Response Message 80 are shown in Table 19 below. TABLE 19 Subscription Update Response Message Attri- Manda- Tag bute(s) Description tory? SubscriptionUpdateResponse Message's abbreviated Yes name senderId val The responding Yes router's id isOk val Boolean value indi- Yes cating whether the update packets were all processed successfully or not

FIG. 21 shows a sample Add Subscriber Request Message 81. The components of the Add Subscriber Request Message 81 are shown in Table 20 below. This message is sent by subscribers of the XML router to the XML router. TABLE 20 Add Subscriber Request Message Attri- Manda- Tag bute(s) Description tory? AddSubscriber Message's abbreviated name Yes senderId val The sending endpoint's unique id No username val The new subscriber's username No password val The new subscriber's password No address val The new subscriber's network Yes address name val The new subscriber's name Yes

FIG. 22 shows a sample Add Subscriber Response Message 82. The components of the Add Subscriber Response Message 82 are shown in Table 21 below. This message is sent by the XML router back to a subscriber of the XML router in response to a received Add Subscriber Request Message. TABLE 21 Add Subscriber Response Message Attri- Manda- Tag bute(s) Description tory? AddSubscriberResponse Message's abbreviated Yes name senderId val The responding router's Yes unique id isOk val Boolean value indicating Yes whether the new subscriber was created or not

FIG. 23 shows a sample Remove Subscriber Request Message 83. The components of the Remove Subscriber Request Message 83 are shown in Table 22 below. This message is sent by subscribers of the XML router to the XML router. TABLE 22 Remove Subscriber Request Message Attri- Manda- Tag bute(s) Description tory? RemoveSubscriber Packets abbreviated name Yes senderId val The sending endpoint's unique No id username val The subscriber's username No password val The subscriber's password No subscriberId val The id of the subscriber to Yes remove

FIG. 24 shows a sample Remove Subscriber Response Message 84. The components of the Remove Subscriber Response Message 84 are shown in Table 23 below. This message is sent by the XML router back to a subscriber of the XML router in response to a received Remove Subscriber Request Message. TABLE 23 Remove Subscriber Response Message Attri- Manda- Tag bute(s) Description tory? RemoveSubscriberResponse Packets abbreviated Yes name senderId val The responding Yes router's unique id isOk val Boolean value indi- Yes cating whether the subscriber was deleted or not

When parsing an IRP protocol message, the following rules must be implemented by the receiver to ensure backwards and forwards compatibility:

-   -   1. If the first (outermost) element (the message type) is not a         recognized message for the protocol (XLSP or XSMP), the message         is discarded. The mandatory attribute, if present on the         outermost element, can be used to indicate whether the sender         indicates this message is mandatory or not to support. Receipt         of a non-understood mandatory message indicates a protocol         error.     -   2. The {“version=x.y”} attribute must be present in the first         element, and is compared to the protocols own internal version         number, p.q, as follows:         -   a. If x.y=p.q, then the protocol versions are the same (both             the major version portion x and the minor version portion             y).         -   b. If x>p, then the received message is of a higher major             version than that supported by the receiving node,             indicating a non-backwards compatible change to the             protocol. The receiver must discard the message, and             preferentially produce a log or alarm to indicate that a             version mismatch exists.         -   c. If x<p, then the received message is of an older version             number than what the node supports, but the major version             number has been changed, indicating a major change to the             protocol which is not backwards compatible. The receiver             must discard the message, and preferentially produce a log             or alarm to indicate that a version mismatch exists.         -   d. if x=p and q>y, then the received message is older than             the local implementation, and backwards compatibility rules             exist for interpreting and handling the message.         -   e. If x=p and y>q, then the received message is newer than             the local implementation (but the major version numbers are             the same), and the receiver will attempt to parse the             message, obeying the rules given in the next two points.     -   3. If a received field is unknown by the receiver (that is, the         XML element name is not recognized), handling of the message is         dependent on the {“mandatory=”} attribute:         -   a. If the field contains a {“mandatory=FALSE”} attribute, or             the {“mandatory”} attribute is omitted, then the receiver             ignores the field, but parses the remainder of the message             as normal.         -   b. If the field contains a {“mandatory=TRUE”} attribute,             then the receiver must discard the message.     -   4. If a particular message field is omitted by the sender, then         the action of the receiver is defined by its internal         {“mandatory”} attribute for that field (ie stored in an internal         data dictionary).         -   a. If the field is tagged as {“mandatory=FALSE”}, then the             receiver assigns a suitable default value to the field.         -   b. If the field is tagged as {“mandatory=TRUE”} attribute,             then the receiver must discard the message.

It should be noted that in the example messages, the first element (the one that defines the message type, such as element 31 of FIG. 4) can also carry the mandatory attribute like any other element. This can indicate to the receiver whether it is a protocol error or not that this new message which is not understood is being discarded.

When a message is discarded, if the message was a request message that is understood by the receiver, then a response message can optionally be sent back indicating that the request message was rejected. The way in which this is done depends upon the exact syntax of the response message. For example, the response message may have an “isOk” tag to carry whether the request message was processed successfully or not.

Note that other encoding schemes of protocol messages are also possible using XML. For example, instead of the outermost XML element indicating the message type, an attribute can carry the message type. It will be appreciated by those skilled in the art that numerous XML encoding schemes can be used to achieve the same result. Also, namespaces could be used for some or all of the XML message tags, including the message type.

An exemplary embodiment of the invention has been described. It will be appreciated by persons skilled in the art that many variants are possible within the scope of the invention.

All references mentioned above are herein incorporated by reference. Reference has been made herein to copending provisional applications, which are incorporated by reference. Such incorporation by reference should also be taken to include the non-provisional applications based thereon whose serial numbers will be inserted when they become available. 

1. A method of controlling communication networks including a plurality of network elements, comprising: encoding control plane protocol messages using a markup language; and transferring said encoded messages between said network elements.
 2. The method of claim 1, wherein said markup language is XML.
 3. The method of claim 2, wherein said messages include a plurality of nested elements.
 4. The method of claim 3, wherein said nested elements include XML tags, attributes reflecting message type and version number, or a combination of XML tags and attributes reflecting message type and version number.
 5. The method of claim 3, wherein the outermost message nested element reflects message type.
 6. The method of claim 4, wherein said nested message includes additional nested elements representing data fields.
 7. The method of claim 6, wherein said additional nested elements are tagged with attributes defining rules associated with that particular field.
 8. The method of claim 7 wherein said rules include parsing and backwards compatibility rules.
 9. The method of claim 4, wherein a network element receiving an incoming message examines said incoming message to determine whether the message type is a recognized message, and if the incoming message is not recognized type discards the incoming message.
 10. The method of claim 9, wherein said network element receiving an incoming message examines said incoming message to determine the version number, and if the incoming message has a version is incompatible with the receiving network element, said receiving network element discards the incoming message.
 11. The method of claim 10, wherein said receiving network element generates a log or alarm in the event of a version mismatch.
 12. The method of claim 1, wherein said messages form part of a link state protocol.
 13. The method of claim 1, wherein said messages form part of a subscription management protocol.
 14. A method of routing in content-based networks including a plurality of XML routers, comprising: assembling routing messages for exchanged between XML routers in the network; encoding said messages using XML; and exchanging said coded messages between said routers.
 15. The method of claim 14, wherein said messages comprise nested elements reflecting data fields.
 16. The method of claim 15, wherein said messages include an XML element indicating protocol message type.
 17. The method of claim 16, wherein said XML element indicating protocol message type is the outermost nested element.
 18. The method of claim 17, wherein the outermost element includes an attribute indicating the version of a protocol employed in the message.
 19. The method of claim 15, wherein each message element is tagged with attributes which define the parsing and backwards compatibility rules for that particular field.
 20. A method of routing packets in a content-based network including a plurality of XML routers, comprising: establishing an XML Link State Protocol and an XML Subscription Management Protocol that routes customer data based on XML content; and exchanging implicit routing protocol (IRP) messages encoded using XML between said routers using said XML Link State Protocol and XML Subscription Management Protocol.
 21. A method as claimed in claim 20, wherein said IRP messages are enclosed within an XML element, and a first level element defines the message type.
 22. A method as claimed in claim 21, wherein said first level elements each include an attribute indicating the version of the protocol.
 23. A method as claimed in claim 22, wherein remaining elements nested within first level elements represent the fields of a given protocol message.
 24. A method as claimed in claim 23, wherein each element is tagged with attributes which define the parsing and backwards compatibility rules for that particular field.
 25. A content router for use in a content routed network, said router being configured to exchange control messages containing control information with other content routers in the network, and said router further being configured to encode said control information using a markup language.
 26. The content router of claim 25, wherein said markup language is XML.
 27. The content router of claim 26, wherein said content router employs an XML link state protocol to manage links within the network and an XML subscription management protocol that routes customer data based on XML content, said content router being configured to employ said control messages as part of said link state protocol and said subscription management protocol. 